1. Field of the Invention
The present invention relates to a cassette supply apparatus that holds documents in a flat state and supplies to an image reading apparatus for reading the documents and converting the documents into electric signals.
2. Description of the Prior Art
In the art of multicolor plate-making, so far, the images are input by using an image reading apparatus and a magnification measuring instrument.
The above image reading apparatus is called a color separation scanner, and works to scan a document such as a two-dimensional color photograph, i.e., reads the document, and outputs electric signals representing the separated colors. The electric signals are used for color printing.
A drum (transparent cylinder) has heretofore been used as means for holding a document to be read by the image reading apparatus. In this case, the document is stuck with an adhesive tape or the like to the peripheral surface of the drum, and then the drum is rotated, so that the document may be read by a sensor.
However, the document-holding device using such a drum involves problems as described below.
That is, the sheet-like document stuck onto the peripheral surface of the drum is curved.
Therefore, the convenience in handling the document is not good, and the expensive drum and document may be damaged.
In particular, the documents which are the properties of clients should never be damaged.
In order to increase the speed of reading the documents, furthermore, the drum must be rotated at high speeds, causing the apparatus to become bulky.
The present applicant therefore has previously proposed an image inputting device (Japanese Utility Model Application No. 170271/1988) using, as a document-holding device, a cassette that holds the planar document as it is, not curved.
The document-holding device using such a cassette enables the planar document to be easily handled in its own form and further enables the document to be read at high speeds without causing the apparatus to become bulky.
The sizes of the aforementioned documents, for example, are of 35 mm, 6.times.9 cm, 4.times.5 in., etc.
The above-mentioned cassettes have heretofore been contained in a container box called stacker 70, as shown in FIG. 16. The stacker 70 is provided with a plurality of stepped portions 70a to contain a plurality of cassettes 71 in the vertical direction.
The stacker 70 is set onto a stacker plate from which the cassettes 71 are supplied one by one to the side of the document plate.
In this case, there is provided with a delivery device which pushes forward the cassettes 71 contained in the stepped portions 70a of the stacker 70 by a pushing member to deliver them successively from the stacker 70, and a sending device which sends the cassettes 71 delivered from the stacker 70 to the side of the image reading apparatus, and returns the cassettes 71 from the side of the image reading apparatus to the stepped portion 70a where the cassette 71 has been initially contained in the stacker 70.
However, the conventional cassette supply apparatus comprising the stacker 70, delivery device and sending device causes the problem mentioned below.
That is, in the conventional stacker 70, a plurality of stepped portions for containing a plurality of cassettes stepwise one by one in the vertical direction are provided, so that the overall height and size become large.
Further, it is necessary to position the cassette when the cassette 71 is taking in and taking out, so that the store of the cassette 71 becomes troublesome.
That is, an operation must be carried out for each delivery of cassette 71 to bring the position of the pushing member into agreement with the stepped portion 70a of the delivered cassette 71 by raising or lowering the stacker 70, and another operation must further be carried out for each delivery of cassette 71 to bring the position of the sending portion of the sending device into agreement with the stepped portion 70a of the returned cassette 71 by raising or lowering the stacker 70.
So far, therefore, it has been necessary to strictly position the pushing member of the sending device at the stepped portion 70a of the cassette 71, and the sending portion of the sending device at the stepped portion 70a of the returned cassette 71. Accordingly, complex control operation has been required to drive the stacker plate for raising or lowering the stacker 70, causing disadvantage in the cost of production.